1. Field of the Invention
The invention relates to a navigation system which displays a guidance based on map data, particularly, that displays on the screen conspicuous roadside structures and buildings as land marks.
2. Description of the Related Art
In recent years, functions in navigation systems have been highly enhanced, in which more multifarious guidance information became available on the screen to navigate drivers on motor vehicles. The guidance information to be displayed generally includes roads in the area of the current position and, in addition, land marks that correspond with roadside facilities and structures. If logos, for instance, to indicate certain facilities such as gas stations and convenience stores are provided and shown to be superimposed in the map, that would be helpful to the drivers in finding the land marks in the course of being navigated.
As recent image processing technology progresses, there are increasing needs for guidance information displayed to be more real. Therefore, it is desirable to use realistic land marks that depict the shapes of actual structures in addition to things like logos.
However, the screen may look awkward when a conventional logo-like land mark is replaced by realistic one. In other words, the land mark may be displayed off the road of actual location, or a part of the building such as an entrance to the building is not set facing the road, which would result in giving the user a strong sense of wrongness. There was a problem that screen configuration was not so simple when a realistic land mark was to be used as it needed to be set correctly in terms of location and direction of the building toward the road, while the angle or location to the road did not have to be set so accurately when the conventional logo-like land marks were used.
The invention, therefore, is designed in consideration of the aforementioned difficulty in order to achieve an objective of providing navigation system that could define the direction and location of land marks accurately toward nearby streets when using realistic land marks.
The above object of the present invention can be achieved by a navigation system of the present invention for displaying guidance in accordance with map data. The system includes a land mark displaying device for displaying structures corresponding to the map data as land marks. The land mark displaying device sets reference positions in the land marks and determines the location and direction of a land mark so that it would face to a road nearby.
According to the present invention, when the land mark is used to display guidance together with map data on a screen in a navigation system, the land mark displaying device sets the location and direction in relation to the reference position to be defined in a land mark. Then, the land mark displaying device displays the land mark arranged so that they come in contact with one of the roads nearby. Therefore, the land mark is displayed in an accurate arrangement with realistic direction and location to the road, and the visibility of the guidance display in the navigation system is upgraded.
In one aspect of the present invention, the landmark displaying device selects a road closest to the land mark when multiple roads exist in areas near to the land mark.
According to this aspect, when multiple roads exist in areas near to the land mark, the landmark displaying device arranges the land mark so that the reference position of the land mark comes to contact with the closest road. Thus, various structures expressed as land marks are arranged accurately on the road and the guidance displayed looks natural.
In another aspect of the present invention, the land mark displaying device sets the priority in accordance with the types of the roads and selects a road with the highest priority when multiple roads exist in areas near to the land mark.
According to this aspect, when multiple roads exist in areas near to the land mark, the land mark displaying device arranges the land mark so that the reference position of the land mark comes to contact with the road with the highest priority. Thus, various structures generally having a high possibility to be located on major roads, for instance, are arranged to depict the reality; thus the guidance displayed looks natural.
In another aspect of the present invention, the land mark includes three-dimensional land marks that three-dimensionally represent structures corresponding to the map data.
According to this aspect, by using the three-dimensional land marks, structures like various facilities are realistically represented and are displayed on the screen with location and direction to the nearby road set as described above. Thus, various facilities are arranged on the road accurately in realistic expression, which resulted in enhancement of visibility of the guidance displayed in the navigation system.
In another aspect of the present invention, when there is not sufficient space to display three-dimensional land marks on the screen, three-dimensional land marks are replaced with plane ones. Thus, the land marks can be identified by the users and the most appropriate guidance to be displayed in accordance with the status of the surroundings even when display space is small with crowded various facilities.